Study on Atomic Layer Deposition of Amorphous Rhodium Oxide Thin Films

Atomic layer deposition (ALD) of rhodium oxide thin films has been studied using Rh(acac)₃ (acac = acetylacetonato) and ozone as precursors. Amorphous Rh₂O₃ thin films were deposited between 160 and 180 °C. The sublimation temperature of Rh(acac)₃ set the low temperature limit for the oxide film deposition, while the high temperature limit was governed by the partial reduction of the film to metallic rhodium. The rhodium oxide films were successfully deposited on Al₂O₃ nucleation layers, soda lime glasses, and native oxide covered silicon substrates. The films demonstrated excellent conformality as characteristic for ALD. The films were not uniform across the substrate, which was most likely due to the catalyzing effect of Rh₂O₃ for ozone decomposition. The nonuniformity was repeatable and could be simply compensated in the cross-flow reactor. By splitting the deposition in two stages with 180° substrate rotation in between, good uniformity across the substrate was accomplished. The resistivities of about 80 nm thick Rh₂O₃ films were from 5 to 8 mΩcm.